1. Field of the Invention
The present invention relates to a lens drive device for driving a lens for a camera.
2. Related Background Art
Patent Literature 1 (International Publication No. 2011/132920 pamphlet) discloses a lens drive device comprising a base, a lens holder, a magnet, an electromagnet, and a case. The lens holder has a cylindrical barrel for holding a lens, first and second projections projecting from the outer peripheral surface of the barrel in a direction intersecting the optical axis, a fixed part fixed on the base and arranged on the opposite side of the barrel from the first and second projections while being separated from the barrel, and first and second joints for joining the first and second projections to the fixed part, respectively.
Each of the first and second joints includes a pair of arm members each having a quadrangular prism form. The pair of arm members extend in parallel with each other between the projection and the fixed part. Each of the end parts of the pair of arm members is made thinner in the optical axis direction. Therefore, the pair of arm members are bendable with respect to the fixed part, while the projection and barrel are bendable with respect to the pair of arm members. The barrel unattached to the base can be translated so as to move closer to and away from the base through the arm members of the joints without substantially tilting the optical axis.
The magnet is attached to a side face of the barrel (the surface of the projection on the opposite side of the barrel). The electromagnet is attached to the base so as to oppose the magnet while being separated therefrom. The case is attached to the base so as to construct an accommodation space with the base, whereby the accommodation space contains therein the lens holder, magnet, and electromagnet.
In thus constructed lens drive device described in Patent Literature 1, the electromagnet operates so as to exert an electromagnetic force between the electromagnet and the magnet. This electromagnetic force translates the barrel so as to make it move closer to and away from the base according to the direction of a current while attracting the lens holder toward the electromagnet.